Process for the preparation of tomato extracts with high content in lycopene

ABSTRACT

A process for the extraction of lycopene from whole tomatoes, in which process tomatoes are heat concentrated and extracted with water-saturated ethyl acetate.

FIELD OF THE INVENTION

The present invention relates to a process for the preparation of tomatoextracts with high content in lycopene.

TECHNICAL BACKGROUND

Lycopene is a natural pigment, particularly abundant in tomatoes andwatermelon, having intense red color. Due to this characteristic, aswell as its safety and beneficial effects, lycopene is widely used inthe food industry as a coloring agent, usually in the form of oleoresin,i.e. a suspension in natural lipids. In this form, lycopene oxidation(crystalline lycopene being highly unstable) and bacterial degradationare prevented, most likely due to the lipids and natural antioxidantspresent. Furthermore, lycopene is used as food supplement thanks to itsantioxidative and chemoprotective properties.

Although lycopene can be prepared by synthesis [Karrer et al., Helv.Chim. Acta 33, 1349 (1950); Isler et al., ibid. 39, 463 (1956)], it isusually obtained by extraction from tomatoes (Lycopersicum esculentum).As lycopene has intense red color only when in the crystalline form, theextraction process should allow to obtain the product in this form.

To date, the suggested methods (WO 95/16363 and WO 97/48287) comprisethe separation of the serum from the pulp, and the extraction of thelatter with solvents. In WO 97/48287 tomatoes, before pulp-serumseparation, which has to be performed under controlled conditions, aresubjected to heat treatment; the extraction is carried out in the hot aswell.

Although these processes may be used with any type of tomatoes, thelycopene starting content should preferably be above 50 ppm.

DETAILED DISCLOSURE OF THE INVENTION

The present invention relates to a process for the preparation of tomatowhole extracts with lycopene content from 5% to 20% and with reducingsugars content, expressed as glucose, below 1%, which process comprisesthe following steps:

a) pretreating fresh tomatoes, which comprises washing, then cutting orcrushing;

b) heat concentrating of the cut or crushed tomato from step a);

c) extracting the concentrate from step b) with water-saturated ethylacetate;

d) backwashing the extract from step c) with water;

e) concentrating the extract to dryness under reduced pressure.

Pre-treatment is carried out according to conventional techniques andany method providing a homogeneous cut/crushed tomato will be suitable.

Concentration (step b) is carried out by distillation under reducedpressure, at temperatures ranging from 40 to 70° C., preferably at 50°C., so that the weight of the cut/crushed tomato will be 20-30% thestarting value.

Extraction of the concentrate (step c) is repeatedly performed withwater-saturated ethyl acetate in a volume ranging from 1.0 to 2.5,preferably 2, times the weight of the concentrate, to obtain alycopene-free residue. According to a preferred embodiment of theinvention, the extraction is repeated four times. The extraction iscarried out for at least one hour at room temperature, shielding fromlight and keeping the concentrate-solvent mixture under stirring.

Each extract is washed with water (step d), preferably in half thevolume of the solvent used for each single extraction, after that theextracts are combined, filtered and evaporated to dryness under reducedpressure (step e). Washing with water is mandatory for the success ofthe process; it has in fact been observed that, when this step isomitted, as illustrated in detail in the subsequent example 3, a higheramount of whole extract is obtained which has however percent lycopenecontent lower by about one third (approximately 4% instead of 6%, fortomatoes containing 50 ppm of lycopene).

Furthermore, the process of the invention allows to obtain crystallinelycopene, with purity higher than 50%, from which the oleoresin can beprepared. For this purpose, steps a)-d) are carried out as describedabove, whereas at step e) the extract is concentrated to a final volumeranging from 0.10 to 0.28% with respect to the starting volume. Theconcentrated extract is then left to stand for some hours and thelycopene crystalline precipitate is filtered off and dried (step f). Theresulting crystalline lycopene may optionally be suspended in ethanol,then filtered and washed with ethyl acetate until obtaining the desiredpurity. The oleoresin is obtained by adding seed oil to the lycopenecrystals, preferably tomato seed oil or soybean oil (step g).

Advantageously, the process according to the present invention providesgood yields even when using tomatoes with low starting content inlycopene and it allows to obtain a whole extract with high lycopenecontent, ranging from 5% to 20%, which is about twice higher thatobtained with the method disclosed in WO 97/48287, as illustrated in theComparison Example below. This process is also advantageous in that thereducing sugars content in the extract is always lower than 1%, usuallylower than 0.5%.

The invention is illustrated in greater detail by means of the followingexamples.

EXAMPLE 1 Preparation of the Extract According to the Invention

52 kg of fresh tomatoes with lycopene content 50 ppm are cut andhomogenized in a blender.

Part of water (34 L) is distilled off under reduced pressure (20 mBar)at 60° C. and discarded, to obtain 17.8 Kg of tomato concentrate.

36 L of water-saturated ethyl acetate are poured on the concentrate andthe mixture is stirred for 2 hours at room temperature, shielded fromlight.

After 2 hours the extract is collected and the residue is extractedagain with 36 L of water-saturated ethyl acetate. The mixture is stirredfor 2 hours at room temperature, shielded from light. The extract isfiltered and washed in a separatory funnel with 18 L of water, which isthen removed and the extract is collected.

Two extractions and two washings as described above are repeated (using144 L of solvent totally). After filtration, the extracts are combinedand concentrated to dryness under reduced pressure; the resulting tomatowhole extract (38.9 g) has HPLC lycopene content of 6.05%, reducingsugars content (expressed as glucose) of 0.28%, phospholipids content of12.97% and mono-di-glycerids content of 24.02%.

EXAMPLE 2

50 kg of fresh tomatoes with lycopene content of 150 ppm are cut andhomogenized in a blender.

Part of water (31 L) is distilled off under reduced pressure (20 mBar)at 60° C. and discarded, to obtain 18.8 Kg of tomato concentrate.

40 L of water-saturated ethyl acetate are poured on the concentrate andthe mixture is stirred for 2 hours at room temperature, shielded fromlight.

After 2 hours the extract is collected and the residue is extractedagain with 40 L of water-saturated ethyl acetate. The mixture is stirredfor 2 hours at room temperature shielded from light. The extract isfiltered and washed in a separatory funnel with 20 L of water, which isthen removed and the extract is collected.

Two extractions and two washings as described above are repeated (using160 L of solvent totally). After filtration, the extracts are combinedand concentrated to dryness under reduced pressure; the resulting tomatowhole extract (37.2 g) has HPLC lycopene content of 17.8% and reducingsugars content (expressed as glucose) of 0.31%.

EXAMPLE 3 Preparation of the Extract without Backwashing with Water

Tomatoes belonging to the same lot as in Example 1, with lycopenecontent of 50 ppm, are used.

4.5 kg of tomatoes are cut and homogenized in a blender, then 3.3 L ofwater are distilled off under reduced pressure (20 mBar) at 60° C.

The resulting concentrate (1.17 kg) is extracted 4 times with 2.3 L eachof (9.2 L of solvent totally), stirring each time for 2 hours at roomtemperature and shielding from light.

The extracts are combined, filtered and concentrated to dryness underreduced pressure. The resulting whole extract (5.09 g) has HPLC lycopenecontent of 4%, reducing sugars content (expressed as glucose) of 4.46%,phospholipids content of 16.51% and a mono-di-glycerids content of14.47%.

EXAMPLE 4 Preparation of the Oleoresin in Tomato Oil

The procedure of Example 1 is followed, but concentrating the combinedextracts to 200 ml final volume. The concentrated extract is left tostand overnight, shielded from light, to obtain a dark red needlecrystal, which is filtered under vacuum, shielding from air, washed withethyl acetate and dried under vacuum at 50° C., to obtain 4.23 g ofcrystalline lycopene with 51% purity.

The crystalline lycopene is added with 6.75 g of tomato seed oil(obtained by hexane extraction) and the mixture is stirred vigorously,to obtain 10.7 g of a fluid, homogeneous, dark red product having 19.8%lycopene content.

EXAMPLE 5 Preparation of the Oleoresin in Soybean Oil

The procedure of Example 1 is followed, but concentrating the combinedextracts to a final volume of 200 ml. The concentrated extract is leftto stand overnight, shielded from light, to obtain a dark red needlecrystal, which is filtered under vacuum, shielding from air, washed withethyl acetate and dried under vacuum at 50° C., to obtain 4.23 g ofcrystalline lycopene with 51% purity.

The crystalline lycopene is added with 6.75 g of soybean oil (obtainedby hexane extraction) and the mixture is stirred vigorously, to obtain10.7 g of a fluid, homogeneous, dark red product having 19.8% lycopenecontent.

EXAMPLE 6 Preparation of 9.5% Purity Lycopene

The procedure of Example 1 is followed, but concentrating the combinedextracts to a final volume of 200 ml. The concentrated extract is leftto stand overnight, shielded from light, to obtain a dark red needlecrystal, which is filtered under vacuum, shielding from air. The solidis suspended in 80 ml of ethyl acetate and heated to 45° C. withstirring for 20 min. The mixture is then left to cool to roomtemperature and filtered under vacuum, shielding from air. The solid issuspended in 200 ml of ethanol and heated to 45° C. with stirring for 10min, then filtered while hot, under vacuum and shielding from air. Thisprocedure is repeated once more. After that, the solid is washed on thefilter with 40 ml of cold ethyl acetate, then dried under vacuum at 50°C., to obtain 2.05 g of crystalline lycopene with 95% purity.

COMPARATIVE EXAMPLE Extraction According to the Method Described in WO95/16363

Tomatoes belonging to the same lot as in Example 1, with lycopenecontent of 50 ppm, are used.

5.14 kg of tomatoes are cut and homogenized in a blender, thencentrifuged at 3000 r for 15′, to separate serum from the insolublefraction (1.315 kg), which is extracted 4 times with 2.65 L each ofethyl acetate (10.6 L of solvent totally), each extraction during 2hours, under stirring, at a temperature of 60° C. and shielding fromlight.

The extracts are combined and concentrated to dryness under reducedpressure. The resulting tomato whole extract (6.07 g) has HPLC lycopenecontent of 3.5%, reducing sugars content (expressed as glucose) of8.74%, phospholipids content of 35.57% and mono-di-glycerids content of12.44%.

1) A process for the preparation of tomato whole extracts with lycopenecontent from 5% to 20% and with reducing sugars content expressed asglucose lower than 1%, comprising the following steps: a) pretreatingfresh tomatoes, which comprises washing, then cutting or crushing; b)heat concentrating of the cut or crushed tomato from step a); c)extracting the concentrate from step b) with water-saturated ethylacetate; d) backwashing the extract from step c) with water; e)concentrating the extract to dryness under reduced pressure. 2) Aprocess as claimed in claim 1, wherein the concentration of the extractaccording to step e) is carried out to a final volume ranging from 0.10to 0.28% with respect to the starting volume, further comprising thefollowing steps: f) filtering and drying the lycopene precipitated fromthe concentrate; and optionally suspending lycopene in ethanol or ethylacetate, then filtering and washing with ethyl acetate until obtainingthe desired purity; g) adding seed oil to lycopene from step f). 3) Aprocess as claimed in claim 2, wherein the seed oil is tomato seed oil.4) A process as claimed in claim 2, wherein the seed oil is soybean oil.5) Tomato whole extracts with lycopene content from 5% to 20% and withcontent in reducing sugars, expressed as glucose, lower than 1%,obtainable with the process of claim 1.